PD-L1 in Breast Cancer: Comparative Analysis of Three Different Antibodies

Publication date: Available online 31 August 2017
Source:Human Pathology
Author(s): Tejashree Karnik, Bruce F. Kimler, Fang Fan, Ossama Tawfik
The Programmed cell death-1 and its ligand-1 (PD-L1) interaction serve as a regulatory check against excessive immune response to antigen and autoimmunity. We compared the performance of three different PD-L1 antibodies (Ventana SP263, Dako 22C3 and BioCare RbMCAL10 antibodies) in 136 invasive ductal carcinoma specimens including 43 primary, 48 locally metastatic and 46 distantly metastatic disease. PD-L1 expression was correlated with clinicopathologic parameters including tumor size, grade, lymphovascular invasion, estrogen receptor (ER), progesterone receptor (PgR), HER2, Ki67, molecular type, TN status. There was excellent agreement between the three antibodies, with highly significant Kappa values (P≤.001). PD-L1 expression was more likely to be associated with higher tumor grade, ER-, PgR-, triple negative (TN) and highly proliferative tumors (P<.001). When we studied PD-L1 expression at 0, 1–9%, 10–49% and ≥50% cutoff points by the three antibodies there were 20 discordant cases between the antibodies. Sixteen were of inconsequential impact as far as low and high PD-L1 expression. The four differences between antibodies did exhibit an interesting pattern of expression, where there was a general agreement between the BioCare and Ventana antibodies with consistent higher PD-L1 expression compared to the Dako antibody. Given the high concordance, it is not surprising that all three antibodies demonstrated the same associations with all pathologic and clinical parameters studied. Standardization studies to identify reliable biomarkers that help in patient selection for immune therapy to improve the risk–benefit ratio for these drugs are still needed.



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